Handbook of Electrical Installation Practice - BeKnowledge

234 Handbook of Electrical Installation Practice
Meter
Lightning protection
to main earth bond
Earth bar
Fig. 9.19 Bonding of incoming services.
Lightning conductor
Connecting clamp
Test joint
Lightning protection earth
termination network
Telephone
service
Electricity
cable
Water
the L-shaped support girders should be used. Cables attached to masts should be
routed within the mast (as opposed to on the outside) to prevent direct current
injection.
Earthing and bonding
Detailed guidance on earthing is beyond the scope of this chapter. Additional and
complementary guidance is given here to improve earthing, and to achieve an area
of equal potential, ensuring that electronic equipment is not exposed to differing
earth potentials and hence resistive transients.
All incoming services (water and gas pipes, power and data cables) should be
bonded to a single earth reference point. This equipotential bonding bar may be the
power earth, a metal plate, or an internal ring conductor/partial ring conductor
inside the outer walls. Whatever form it takes, this equipotential bonding bar should
be connected to the electrode(s) of the earthing system. All metal pipes, power and
data cables should, where possible, enter or leave the building at the same point, so
that extraneous metalwork and armouring can be bonded to the main earth terminal
at this single point (Fig. 9.19). This will minimise lightning currents within the
building.
Gas